1. Field of the Invention
The present invention relates generally to valves and valve systems, and more particularly, to a valve fitting configured to limit pressure exerted upon a valve surface by a fitting's sealing surface so as to inhibit the sealing surface from deforming and thereby causing the valve to leak.
2. Description of Related Art
Valves and valve systems are well known for halting and controlling the flow of fluids through a passage, such as a pipe. A valve typically includes a device, such as a disk that is configured to mate with a valve seat. The device operates to seal an aperture through the valve seat. The disk is actuated in order to open and partially or wholly close the aperture and thereby control the fluid flow through the valve.
One common embodiment of valve devices is know as a ball type valve. Ball valves comprise a spherical plug or "ball shaped valve" and an annular valve seat that mates with the ball valve. The characteristic feature of the ball valve is that the surfaces of the annular valve seat and ball valve are surfaces of revolution, so that there is a negligible amount of thrusting force acting in the direction of the valve stem.
In ball valves that are intended for high pressure applications, the ball member is often trunnion supported with valve seats or seat rings. The valve seats or valve rings have the capability of floating and being pressure activated to seal against the ball. In larger dimensioned high pressure ball valves, means are typically provided to limit the amount of fluid pressure that acts on the seats. This prevents the imposition of destructively high compressive stress against the ball valve.
One such ball valve is disclosed in U.S. Pat. No. 4,479,513, by Koch et al., and U.S. Pat. No. 4,572,239, by Koch et al. Each of the Koch patents discloses a ball valve designed for high pressure shut-off at fluid pressures approaching the ultimate compressive stress of plastic annular seats that are employed in the valve. The ball member is trunnion mounted in order to carry the total force of the shut-off pressure. The seat rings are disposed in seat carriers. Each seat ring includes a spherical ball engaging surface having a radius slightly less that the radius of the ball.
In Koch, each carrier is continuously urged toward the ball by a plurality of disc springs in order that the seat ring engaging surfaces will be in continuous sealing engagement with the ball surface. The seat ring is configured so that the areas thereof located adjacent to the outer diameters of the ball are the first to engage the ball. The valve components are configured to limit the effective area that the fluid pressure may act on in urging the seat rings into the ball contact. Thus the compressive stress that is exerted on the plastic annular ring seat material is controlled.
U.S. Pat. No. 4,651,775, to Okada, also discloses a three-way ball valve. The disclosed valve includes a flow controlling ball valve of a hollow mushroom-like construction consisting of a spherical part and a cylindrical part. The Okada ball valve is configured to allow two fluids to flow side by side through half-cylindrical rooms of the valve and flow outward through holes in the half-cylindrical rooms for mixing of the two fluids. The mixed fluids then pass out through an outlet passage of the valve.
Often a fluid conduit, such as a pipe or tubing, is coupled to an outlet or an inlet of the valve body. A threaded fitting may be secured to an end of the conduit then threaded into an inlet or outlet aperture of the body for coupling the conduit to the valve body. However, the fitting must be threaded into the aperture under precise pressure to couple the fitting to the body. Coupling the fitting to the body under excessive pressure may cause a sealing surface of the fitting to distort, or deform, against the internal componentry of the valve. This distortion or deformation of the sealing surface can cause gaps between the sealing surface and componentry, causing the valve to leak and yielding inaccurate fluid volume and flow control. Coupling the fitting to the body under insufficient pressure may also leave a gap between the fitting and the valve, which can also cause the valve to leak. Even a minor amount of leakage and incorrect fluid volume throughflow is unacceptable in certain usages such as in the medical, biological and chemical fields.
Thus, there exists the need for a valve fitting that may be coupled to a valve body which fitting limits the pressure exerted upon sealing surface of the fitting. Such a fitting would inhibit the sealing surface from deforming which may cause the valve to leak and the fluid volume flow through to be inaccurate.